Feeding unit and image forming apparatus having the same

ABSTRACT

Disclosed herein are a printing media feeding unit and an image forming apparatus having the same. The feeding unit may include a feeding roller and a reverse roller arranged parallel to, and to opposingly face, each other. The feeding roller may be supported on a feeding shaft so as to rotate together with the feeding shaft. The reverse shaft may be supported on a reverse shaft so as to rotate together with the reverse shaft. The reverse shaft is arranged to be movable along the radial direction in compensation of the radial movement of the reverse roller with respect to the feed roller that may result from the friction between printing media and the reverse roller so as to improve the performance of the reverse roller in returning of extraneous sheets of printing media to prevent simultaneous feeding of multiple sheets of printing media.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Korean Patent Application No. 2008-0129824, filed on Dec. 19, 2008 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates generally to a feeding unit that feeds one sheet of paper at a time, and an image forming apparatus having the same.

BACKGROUND OF RELATED ART

Image forming apparatuses can be used to print an image on a printing medium, such as paper, for example, based on input image signals. Examples of image forming apparatuses include printers, copiers, facsimiles and so-called multifunctional apparatuses that combine some of the functionalities of the aforementioned apparatuses.

An image forming apparatus typically includes a main body or frame that defines the overall external appearance of the image forming apparatus. Various components and devices that are employed in forming an image on a printing medium, e.g., sheets of paper, may be housed or supported in the main body. For example, an image forming apparatus may have housed in its main body a printing media transport mechanism that may include a print media storage unit for storing print media, e.g., sheets of paper, a pickup unit for picking up the paper stored in the print media storage unit one sheet at a time and a feeding unit for conveying the picked up sheet of the paper to the printing device that may also be housed in the main body.

There are various types of printing device available for use in an image forming apparatus. One example of such printing device type may be a so-called electrophotographic type printing device that generally uses a developing unit that develops an electrostatic latent image formed as potential difference on a photo conductor into a visible image using developer, e.g., toner. Such an electrophotographic type printing device also typically employs a transfer unit for affecting the transfer of the visual toner image from the photo conductor to a printing medium received from the printing media transport mechanism, a fusing unit for fusing the toner image onto the printing medium, typically by the use of heat and pressure. An exit unit of such image forming apparatus then discharge the printing medium onto which the toner image is fused paper out of the main body.

Another type of printing device may be a so-called inkjet type that forms the images of print media by jetting a pattern of droplets of ink through tiny nozzles formed on a printhead onto a printing medium. There are other types printing devices in addition to the above examples.

An image forming apparatus may include a feeding unit for conveying a picked up printing medium along a feed path toward the printing device of any available type. A feeding unit to that end may include a feeding roller and a reverse roller arranged parallel to, and opposingly facing, each other. The two rollers may respectively be disposed on rotational shafts, and may each rotate about the respective shaft receiving the rotary force form the shaft. When multiple sheets of paper are presented simultaneously at the gap between the feeding roller and the reverse roller, the rollers are arranged in such a manner to allow one, typically the top most, sheet to be fed toward the printing device, returning the remaining sheets back to the print media storage unit by the rotation of the reverse roller.

The shafts for the feeding and reverse rollers may each be in a cantilever arrangement, in which one end of the shaft is generally supported on a frame structure while the other end has the roller disposed thereon. In particular, the shaft of the reverse roller may experience a twisting force when the roller end rotates due to the friction between the reverse roller and the sheets of paper, which may result in the reverse roller tilting away from the feeding roller. In such a state, the amount of force imparted on one axial end of the shaft may be different from at the force exerted on the other end. Such difference in the forces may hamper the performance of the reverse roller in effectively sending back the remaining sheets to the print media storage unit.

SUMMARY OF THE DISCLOSURE

In accordance with one aspect of the present disclosure, a feeding unit usable for feeding a printing medium along a printing medium feed path in an image forming apparatus may be provided to comprise a feeding roller, reverse roller, a feeding shaft and a reverse shaft. The feeding roller and the reverse roller may be arranged parallel to each other. The feeding shaft may support thereon the feeding roller, and may be rotatable so as to rotate the feeding roller. The reverse shaft may support at a first end thereof the reverse roller, and may be rotatable so as to rotate the reverse roller. The second end opposite the first end of the reverse shaft may be movably supported such that the second end of the reverse shaft is moveable along a radial direction substantially perpendicular to an axial direction about which the reverse shaft rotates.

The feeding unit may further comprise a frame member that may have an elongated opening, into which the second end of the reverse shaft may be received, and along which the second end of the reverse shaft may move in the radial direction.

The feeding unit may further comprise a reverse driving gear, a reverse driven gear and a reverse belt. The reverse driving gear may be arranged to receive a rotary force from a rotational force source. The reverse driven gear may be installed adjacent the second end of the reverse shaft. The reverse belt may be rotatably supported on the reverse driving gear and the reverse driven gear.

The feeding unit may further comprise an idle roller that may support the reverse belt in such a manner maintaining a tension in the reverse belt.

According to another aspect of the present disclosure, and image forming apparatus may be provided to comprise a feeding unit configured to feed paper a printing medium along a printing medium feed path within the image forming apparatus. The feeding unit may comprise a feeding roller, reverse roller, a feeding shaft and a reverse shaft. The feeding roller and the reverse roller may be arranged parallel to each other. The feeding shaft may support thereon the feeding roller, and may be rotatable so as to rotate the feeding roller. The reverse shaft may support at a first end thereof the reverse roller, and may be rotatable so as to rotate the reverse roller. The second end opposite the first end of the reverse shaft may be movably supported such that the second end of the reverse shaft is moveable along a radial direction substantially perpendicular to an axial direction about which the reverse shaft rotates.

The image forming apparatus may further comprise a pair of elastic members that may be disposed to elastically bias the reverse shaft at locations along the reverse shaft adjacent each of two axial ends of the reverse roller.

The image forming apparatus may further comprise a pair of support members each having a support indentation into which the reverse shaft is received, and may be elastically supported by a respective corresponding one of the pair of elastic members.

According to yet another aspect of the present disclosure, an apparatus for feeding a printing medium along a printing medium feed path of an image forming apparatus. The apparatus may comprise a feeding roller and a reverse roller. The feeding roller may be supported on a feeding shaft, which may be rotatable so as to rotate the feeding roller in a first rotational direction. The reverse roller may extend parallel to, and opposingly facing, the feeding roller, and may be supported at a first axial end of a reverse shaft in such a manner to be rotatable about a rotational axis common to the reverse roller and the reverse shaft in a second rotational direction opposite the first rotational direction. The second end opposite the first end of the reverse shaft may be movably supported such that the second end of the reverse shaft is moveable in a radially outward direction substantially perpendicular to the rotational axis and away from the feeding shaft.

The reverse shaft may be moveable between at least a first position and a second position, and may be substantially parallel to the feeding shaft in each of the first and second positions.

The apparatus may further comprise a frame having an elongated opening, into which the second end of the reverse shaft may be received, and along which the second end of the reverse shaft may move in the radially outward direction.

The apparatus may further comprise a driving gear, a driven gear and a belt. The driving gear may be arranged to receive a rotary force. The driven gear may be coupled to the reverse shaft adjacent the second end of the reverse shaft so as to be rotatable with the reverse shaft. The belt may be rotatably supported on both the driving gear and the driven gear and configured to thereby convey the rotary force from the driving gear to the driven gear.

The apparatus may further comprise an idle roller supporting the belt and to thereby maintain a tension in the belt.

The apparatus may further comprise an elastic members elastically biasing the reverse shaft toward the feeding roller.

The elastic member may comprise a first elastic member arranged at a first location along the reverse shaft adjacent a first axial end of the reverse roller and a second elastic member arranged at a second location along the reverse shaft adjacent a second axial end opposite the first axial end of the reverse roller.

The apparatus may further comprise a support member that includes a support surface having a shape corresponding to the reverse shaft so as to support thereon the reverse shaft, the support member elastically supporting the support member.

BRIEF DESCRIPTION OF THE DRAWINGS

Various aspects and advantages of the present disclosure will become apparent and more readily appreciated from the following description of several embodiments thereof, taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a side cross-sectional view schematically illustrating the configuration of an image forming apparatus in accordance with an embodiment of the present disclosure;

FIGS. 2 and 3 are perspective views of a feeding unit in accordance with an embodiment of the present disclosure; and

FIG. 4 is a plane view illustrative of the operation of the feeding unit in accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION OF SEVERAL EMBODIMENTS

Reference will now be made in detail to several embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. While the embodiments are described with detailed construction and elements to assist in a comprehensive understanding of the various applications and advantages of the embodiments, it should be apparent however that the embodiments can be carried out without those specifically detailed particulars. Also, well-known functions or constructions will not be described in detail so as to avoid obscuring the description with unnecessary detail. It should be also noted that in the drawings, the dimensions of the features are not intended to be to true scale and may be exaggerated for the sake of allowing greater understanding.

As shown in FIG. 1, an image forming apparatus 100 in accordance with an embodiment of the present disclosure may include a main body 10 defining an overall external appearance of the image forming apparatus 100, a print media storage unit 20 that may be detachably received in the main body 10 for storing therein print media P, a pickup unit 30 configured to pick up the print media P from the print media storage unit 20, a feeding unit 40 configured to feed the print media P picked up by the pickup unit 30 one sheet at a time. According to an embodiment, the image forming apparatus 100 may further include a printing unit for carrying out the image forming operations, which may include, for example, a developing unit 50 configured to form a visible image with developer on the sheet of print media P received from the feeding unit 40, an exposure unit 60 configured to form an electrostatic latent image on a photo conductor 51 of the developing unit 50, a fusing unit 70 to fuse the visible imaged formed of developer onto the sheet of printing media P and an exit unit 80 configured to discharge the sheet of printing media P, on which the visible developer image has been fused, out of the main body 10.

The print media storage unit 20 may include a print media cassette 21 received in the main body 10, e.g., as a drawer type that slides in and out of the main body 10, and a knock-up plate 22 disposed in the print media cassette 21 to define a supporting surface on which the print media P received in the print media cassette 21 may be supported.

The pickup unit 30 may be configured to pick up the uppermost sheet of the print media P stacked in the print media storage unit 20, and to convey the picked up sheet of print media P to the feeding unit 40. The pickup unit 30 may include a pickup roller 31 rotatable to come into a frictional contact with, and to thereby pick up, a print medium P stored in the print media storage unit 20.

The developing unit 50 may be operable to form a visible developer image on the print medium P received from the print media storage unit 20. The developing unit 50 may include the photo conductor 51 having a photosensitive surface, on which an electrostatic latent image may be formed by being exposed to light received from the exposure unit 60, a charging roller 52 configured to charge the photo conductor 51 and a developing roller 53 configured to develop the electrostatic latent image formed on the photo conductor 51 into a visible developer image. A transfer roller 11 disposed to oppose the photo conductor 51 may be configured to presses the print medium P against the photo conductor 51 so as to transfer the visible developer image from the photo conductor 51 to the print medium P.

The exposure unit 60 may be configured to irradiate light modulated with image data onto the photo conductor 51, and to thereby form the electrostatic latent image on the photo conductor 51.

The fusing unit 70 may fuse or fix the developer image, which had been transferred from the photo conductor 51, onto the print medium P by applying heat and pressure. The fusing unit 70 may include a heating roller 72 provided with a heater 71 installed therein and a pressure roller 73 to press the paper P onto the heating roller 72. The printing medium P passing through a gap between the heating roller 72 and the pressure roller 73 receives heat and pressure so that the visible developer image carried on the paper P becomes fused to the printing medium P.

The exit unit 80 may include several sequentially arranged exit rollers 81 that operate to discharges the printing medium P that has passed through the fusing unit 70 out of the main body 10. The various units such as the print media storage unit 20, the pick up unit 30, developing unit 50, the exposure unit 60, the fusing unit 70 and the exit unit 80 described above are merely examples in order to illustrate possible configurations of image forming apparatuses in which the feeding unit 40 according to various aspects of the present disclosure may be employed, and should not be construed as limiting the scope of the present disclosure to any particular configuration of an image forming apparatus.

As shown in FIGS. 2 and 3, a feeding unit 40 according to an embodiment may include a feeding roller 41 arranged to rotate about a feeding shaft 42 so as to feed the printing medium P in the forward feeding direction. The feeding roller 41 may be disposed on one end of the feeding shaft 42 that conveys the rotary force to the feeding roller 41. The feeding unit 40 may also include a reverse roller 43 arranged parallel with the feeding roller 41 and to rotate about a reverse shaft 44 in the reverse direction, i.e., the opposite the forward feeding direction. The reverse roller 43 may be disposed on an end of the reverse shaft 44, and may receive the rotary force therefrom.

According to an embodiment, a torque limiter (not shown) may be provided in the reverse roller 43 that causes the reverse roller 43 to rotate in the reverse feeding direction when the reverse roller 43 is subjected to a torque of a designated level or less, and that causes the reverse roller 43 to rotate in the forward feeding direction of the printing medium P when the reverse roller 43 is subjected to a torque of the designated degree or more. With such a configuration, if multiple sheets of printing media P enter the gap between the feeding roller 41 and the reverse roller 43, the reverse roller 43 may serve to return the sheets of printing media P contacting the reverse roller 43 to the print media storage unit 20, and, if one sheet of paper P enters the gap between the feeding roller 41 and the reverse roller 43, the reverse roller 43 is supported by the rear surface of the sheet of printing media P fed by the feeding roller 41 to thereby receive a torque of designated degree or more, and may thus rotate in the forward feeding direction. That is, the reverse roller 43 may prevent multiple sheets of the printing media P from being simultaneously fed through the feeding unit 40, and may thus allow one sheet of the printing media P to be fed to the developing unit 50 at a time.

Referring to FIG. 2, according to an embodiment, the feeding shaft 42 and the reverse shaft 44 may receive the respective rotary forces from a driving motor 13 through a plurality of gears 14 a, 14 b, 14 d and 14 e. A frame 12, on which the driving motor 13 and the gears 14 a, 14 b, 14 d and 14 e are installed, may be disposed at one side in the main body 10. One end of each of the feeding shaft 42 and the reverse shaft 44 may be supported by the frame 12 while the feeding roller 41 and the reverse roller 43 are respectively installed at the other ends of the feeding shaft 42 and the reverse shaft 44.

The frictional force between printing media P and the reverse roller 43 during the process of passing a printing medium P through the gap between the feeding roller 41 and the reverse roller 43 may cause the reverse shaft 44 to become tilted relative to the feeding shaft 42, or otherwise subject the ends of the reverse roller 43 to forces that are respectively different from one another, which may result in the reverse roller 43 not performing effectively in returning the printing media P, for example, a slippage between the printing media and the reverse roller 43 may occur

According to an aspect of the present disclosure, the reverse shaft 44 may be installed in such a manner that it is capable of moving in the radial direction of the feeding shaft 42 to allow the reverse roller 43 to effectively return sheets of the printing media P. That is, according to an embodiment, for example, a guide hole 12a that extends along the radial direction of the feeding shaft 42 may be provided to allow the end of the reverse shaft 44 rotatably supported on the frame 12 to move along the radial direction of the feeding shaft 42 within the guide hole 12 a.

With the above configuration, when a force is applied to the reverse roller 43 due to the friction between the paper P and the reverse roller 43, the reverse shaft 44 may move along the guide hole 12 a as shown in FIG. 4 so that the reverse shaft 44 may be substantially parallel to the feeding shaft 42, which may result in a substantially uniform distribution of the force across the entire region of the reverse roller 43 so that the returning of the sheets of the printing media P by the reverse roller 43 may be effectively carried out.

With reference to FIGS. 2 and 4, the image forming apparatus 100 in accordance with an embodiment may further include one or more elastic support units 90 provided at one or both sides of the reverse roller 43 to elastically support the reverse shaft 44 so as to assist the reverse roller 43 to remain substantially parallel to the feeding roller 41. Each of the elastic support units 90 may include a support member 91 provided with a support indentation 91 a formed in a shape corresponding to the shape of the reverse shaft 44 to rotatably support the reverse shaft 44 and a spring 92 to elastically support the support member 91. According to an embodiment, when two elastic support units 90 are provided to support both sides of the reverse roller 43 through the reverse shaft 44, it may be advantageously possible to more effectively maintain the reverse roller 43 parallel to the feeding roller 41.

According to an embodiment, the feeding shaft 42 may receive the rotary force of the driving motor 13 through a feeding gear 45 installed at one end of the feeding shaft 42. The feeding gear 45 may in turn receive the rotary force of the driving motor 13 through the gears 14 a, 14 b and 14 c. The reverse shaft 44 may receive the rotary force of the driving motor 13 through a reverse driving gear 46, which may in turn receive the rotary force from the driving motor 13 through the gears 14 a, 14 d, 14 e, a reverse driven gear 47 installed at one end of the reverse shaft 44 and a reverse belt 48 that includes a timing belt wound on the reverse driving gear 46 and the reverse driven gear 47. This structure of the reverse shaft 44 may allow the reverse shaft 44 to continuously receive the rotary force from the driving motor 13 while the reverse shaft 44 moves along the radial direction of the feeding shaft 42. According to an embodiment, in order to uniformly maintain the tension of the reverse belt 48, one part of the reverse belt 48 may be supported by an idle roller 49.

As can be appreciated from the above descriptions, in the feeding unit and the image forming apparatus having the same in accordance with one or more embodiments of the present disclosure, the reverse shaft may be capable of moving in the radial direction of the feeding roller shaft so that, when the frictional force between paper and the reverse shaft causes a movement of the reverse roller in the radial direction, the reverse shaft may be capable of moving together with the reverse roller, allowing the reverse roller shaft to remain substantially parallel to the feeding shaft, thereby achieving an effective returning of sheets of the printing media by the reverse roller.

Although several embodiments of the present disclosure have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the disclosure, the scope of which is defined in the claims and their equivalents. 

1. A feeding unit for feeding a printing medium along a printing medium feed path in an image forming apparatus, comprising: a feeding roller and a reverse roller arranged parallel to each other; a feeding shaft supporting thereon the feeding roller, the feeding shaft being rotatable so as to rotate the feeding roller; and a reverse shaft supporting at a first end thereof the reverse roller, the reverse shaft being rotatable so as to rotate the reverse roller, wherein a second end opposite the first end of the reverse shaft being movably supported such that the second end of the reverse shaft is moveable along a radial direction substantially perpendicular to an axial direction about which the reverse shaft rotates.
 2. The feeding unit according to claim 1, further comprising: a frame member having an elongated opening, into which the second end of the reverse shaft is received, and along which the second end of the reverse shaft moves in the radial direction.
 3. The feeding unit according to claim 1, further comprising: a reverse driving gear arranged to receive a rotary force from a rotational force source; a reverse driven gear installed adjacent the second end of the reverse shaft; and a reverse belt rotatably supported on the reverse driving gear and the reverse driven gear.
 4. The feeding unit according to claim 3, further comprising an idle roller supporting the reverse belt and to thereby maintain a tension in the reverse belt.
 5. An image forming apparatus, comprising: a feeding unit configured to feed paper a printing medium along a printing medium feed path within the image forming apparatus, the feeding unit comprising: a feeding roller and a reverse roller arranged parallel to each other; a feeding shaft supporting thereon the feeding roller, the feeding shaft being rotatable so as to rotate the feeding roller; and a reverse shaft supporting at a first end thereof the reverse roller, the reverse roller being rotatable so as to rotate the reverse roller, wherein a second end opposite the first end of the reverse shaft being movably supported such that the second end of the reverse shaft is moveable along a radial direction substantially perpendicular to an axial direction about which the reverse shaft rotates.
 6. The image forming apparatus according to claim 5, further comprising: a frame having an elongated opening, into which the second end of the reverse shaft is received, and along which the second end of the reverse shaft moves in the radial direction.
 7. The image forming apparatus according to claim 5, further comprising: a reverse driving gear arranged to receive a rotary force from a rotational force source; a reverse driven gear installed adjacent the second end of the reverse shaft; and a reverse belt rotatably supported on the reverse driving gear and the reverse driven gear.
 8. The image forming apparatus according to claim 7, further comprising an idle roller supporting the reverse belt and to thereby maintain a tension in the reverse belt.
 9. The image forming apparatus according to claim 5, further comprising: a pair of elastic members disposed to elastically bias the reverse shaft at locations along the reverse shaft adjacent each of two axial ends of the reverse roller.
 10. The image forming apparatus according to claim 9, further comprising: a pair of support members each having a support indentation into which the reverse shaft is received, each of the pair of support members being elastically supported by a respective corresponding one of the pair of elastic members.
 11. An apparatus for feeding a printing medium along a printing medium feed path of an image forming apparatus, comprising: a feeding roller supported on a feeding shaft, the feeding shaft being rotatable so as to rotate the feeding roller in a first rotational direction; and a reverse roller extending parallel to, and opposingly facing, the feeding roller, the reverse roller being supported at a first axial end of a reverse shaft in such a manner to be rotatable about a rotational axis common to the reverse roller and the reverse shaft in a second rotational direction opposite the first rotational direction, wherein a second end opposite the first end of the reverse shaft being movably supported such that the second end of the reverse shaft is moveable in a radially outward direction substantially perpendicular to the rotational axis and away from the feeding shaft.
 12. The apparatus of claim 11, wherein the reverse shaft is moveable between at least a first position and a second position, the reverse shaft being substantially parallel to the feeding shaft in each of the first and second positions.
 13. The apparatus of claim 11, further comprising: a frame having an elongated opening, into which the second end of the reverse shaft is received, and along which the second end of the reverse shaft moves in the radially outward direction.
 14. The apparatus of claim 11, further comprising: a driving gear arranged to receive a rotary force; a driven gear coupled to the reverse shaft adjacent the second end of the reverse shaft so as to be rotatable with the reverse shaft; and a belt rotatably supported on both the driving gear and the driven gear and configured to thereby convey the rotary force from the driving gear to the driven gear.
 15. The apparatus of claim 14, further comprising an idle roller supporting the belt and to thereby maintain a tension in the belt.
 16. The apparatus of claim 11, further comprising: an elastic members elastically biasing the reverse shaft toward the feeding roller.
 17. The apparatus of claim 16, wherein the elastic member comprises a first elastic member arranged at a first location along the reverse shaft adjacent a first axial end of the reverse roller and a second elastic member arranged at a second location along the reverse shaft adjacent a second axial end opposite the first axial end of the reverse roller.
 18. The apparatus of claim 16, further comprising: a support member that includes a support surface having a shape corresponding to the reverse shaft so as to support thereon the reverse shaft, the support member elastically supporting the support member. 